Name 'Key' not defined Lambda function to access DynamoDB - python-3.x

Question

I am using the query function from the boto3 library in Python and receiving the following error:
name 'Key' is not defined: NameError
Traceback (most recent call last):
File "/var/task/lambda_function.py", line 51, in lambda_handler
if not getAssetExistance(slack_userID):
File "/var/task/lambda_function.py", line 23, in getAssetExistance
response = dynamoTable.query(KeyConditionExpression=Key('userID').eq(asset))
NameError: name 'Key' is not defined
I have been reading through a bunch of tutorials on accessing DynamoDB through Lambda, and this they all use this KeyConditionExpression line when trying to if a key exists.
Here is the relevant code (line 23 is the query line):
def getAssetExistance(asset):
dynamoTable = dynamo.Table('Assets')
response = dynamoTable.query(KeyConditionExpression=Key('userID').eq(asset))
return bool(response)
I basically want to check the primary partition key in my DynamoDB table (which is a slack user ID) and see if exist.
Here is the rest of the code if it is relevant:
################################
# Slack Lambda handler.
################################
import boto3
import logging
import os
import urllib
# Grab data from the environment.
BOT_TOKEN = os.environ["BOT_TOKEN"]
ASSET_TABLE = os.environ["ASSET_TABLE"]
REGION_NAME = os.getenv('REGION_NAME', 'us-east-1')
dynamo = boto3.resource('dynamodb', region_name=REGION_NAME, endpoint_url="https://dynamodb.us-east-1.amazonaws.com")
# Define the URL of the targeted Slack API resource.
SLACK_URL = "https://slack.com/api/chat.postMessage"
def getAssetExistance(asset):
dynamoTable = dynamo.Table('Assets')
response = dynamoTable.query(KeyConditionExpression=Key('userID').eq(asset))
return bool(response)
def lambda_handler(data, context):
# Slack challenge answer.
if "challenge" in data:
return data["challenge"]
# Grab the Slack channel data.
slack_event = data['event']
slack_userID = slack_event["user"]
slack_text = slack_event["text"]
channel_id = slack_event["channel"]
slack_reply = ""
# Ignore bot messages.
if "bot_id" in slack_event:
slack_reply = ""
else:
# Start data sift.
if slack_text.startswith("!networth"):
slack_reply = "Your networth is: "
elif slack_text.startswith("!price"):
command,asset = text.split()
slack_reply = "The price of a(n) %s is: " % (asset)
elif slack_text.startswith("!addme"):
if not getAssetExistance(slack_userID):
slack_reply = "Adding user: %s" % (slack_userID)
dynamo.update_item(TableName=ASSET_TABLE,
Key={'userID':{'S':'slack_userID'}},
AttributeUpdates= {
'resources':{
'Action': 'ADD',
'Value': {'N': '1000'}
}
}
)
else:
slack_reply = "User %s already exists" % (slack_userID)
# We need to send back three pieces of information:
data = urllib.parse.urlencode(
(
("token", BOT_TOKEN),
("channel", channel_id),
("text", slack_reply)
)
)
data = data.encode("ascii")
# Construct the HTTP request that will be sent to the Slack API.
request = urllib.request.Request(
SLACK_URL,
data=data,
method="POST"
)
# Add a header mentioning that the text is URL-encoded.
request.add_header(
"Content-Type",
"application/x-www-form-urlencoded"
)
# Fire off the request!
urllib.request.urlopen(request).read()
# Everything went fine.
return "200 OK"
My DynamoDB table is named 'Assets' and has a primary partition key named 'userID' (string).
I am definitely still new to all this, so don't be afraid of calling me a dummy. Any and all help is appreciated. The goal of this code is to check if a user exists as a key in DynamoDB and if not, add them to the table.

Answer 1

You need to import the Key function, like so:
from boto3.dynamodb.conditions import Key

Answer 2

Without importing it second time, u can address it like:
boto3.dynamodb.conditions.Key
def getAssetExistance(asset):
dynamoTable = dynamo.Table('Assets')
response = dynamoTable.query(KeyConditionExpression= boto3.dynamodb.conditions.Key('userID').eq(asset))
return bool(response)

Answer 3

Wrote the below code for getting data from dynamo db and got the error 'NameError: name 'Key' is not defined'.
I had to fix it by importing 'from boto3.dynamodb.conditions import Key'
response = dynamo_table.query(KeyConditionExpression=Key(val).eq(str(key_dictionary[val])))